1. Field of the Invention
This invention is directed in general to the field of audiological testing for human or animal patients, and more particularly to systems for conducting multiple diagnostic hearing tests to assess and analyze hearing loss in human patients. Systems of the invention provide an apparatus for reliably determining the air-conduction and bone-conduction hearing thresholds of a patient, and for conducting one or more additional tests involving acoustic immittance, otoacoustic emission, speech recognition threshold and speech discrimination. The systems further comprise components for performing such tests.
2. Description of the Related Art
Recent studies suggest that over 20 million people in the United States alone have some degree of hearing loss. The number of people worldwide who have some degree of hearing deficit is estimated to be much greater. Not surprisingly, many hearing-impaired people are unaware that they have suffered a decrease in hearing capacity. Because of the complexity of the hearing process itself, decreased hearing capacity may involve any of several factors, including age, health, occupation, injury, disease, and exposure to ototoxic agents, including some antibiotics. This loss of hearing can lead to significant reductions in quality of life, impaired relationships, reduced access to employment and diminished productivity.
Failure to treat the hearing loss may worsen its impact not only on the quality of life of the patient but also on economic productivity as a whole. According to the Better Hearing Institute, the annual cost in the United States in terms of lost productivity, special education, and medical care because of untreated hearing loss is approximately $56 billion. Much of this staggering cost could be reduced or prevented by early detection and treatment. Unfortunately, few people obtain regular and frequent hearing tests as a part of their routine healthcare due, at least in part, to the lack of a simple, convenient, and relatively inexpensive system for conducting hearing tests.
Traditionally, hearing tests are conducted in a clinical setting by a hearing health professional, such as an audiologist, who administers the hearing tests manually. In perhaps the most common type of testing, the hearing health professional controls an audiometer to produce a series of tones that each have a very specific frequency and intensity. The term “intensity” as used herein refers to the amplitude of the tone and is usually given in decibels (dB), expressed either as Sound Pressure Level (dB SPL), which is a logarithmic scale ratio of the intensity of a sound relative to a threshold value, usually 2×10−2 N/m2, or Hearing Level (db HL), which is a value normalized for a particular frequency to the threshold for patients with normal hearing. See, e.g., Gelfand, S., Essentials of Audiology, 2d ed., chapters 1, 3–6, Thieme Medical Publishers, Inc. (2001).
Because each of the tones has a specific frequency and intensity, this type of testing is known as “pure-tone” air conduction audiometry or “pure-tone threshold testing” for air conduction. Threshold testing may also be performed for bone conduction hearing and for speech recognition. In addition, related tests to determine speech discrimination capacity may also be performed. The foregoing types of testing, which involve providing a sound, such as a pure tone or speech, to the ear of the patient and determining whether the patient can hear or distinguish the sound, are referred to collectively as “audiometry,” or “audiometric testing.” Thus, air-conduction threshold, bone-conduction threshold, speech recognition threshold and speech discrimination tests are specific audiometric tests. Other types of hearing testing include acoustic immittance testing, which includes tympanometric testing and acoustic reflex testing, and otoacoustic emission testing. Such tests are well known in the art of hearing testing and are commonly performed by hearing health professionals.
In the typical manual protocol for pure-tone air-conduction threshold testing, electrical signals produced by the audiometer are converted into the desired pure tones by a transducer, such as earphones or ear inserts, located at or immediately adjacent to the ear of the patient, who is sequestered in a quiet room or sound isolation booth. For each audible tone, the patient gestures or otherwise indicates that he has heard the tone. If the tone is not audible, the patient does not respond. The hearing health professional thereafter adjusts the intensity level of the tone in preset increments until it becomes audible to the patient. By repeating this process for several different tones and compiling the results, the hearing health professional is able to determine the deviation of the patient's hearing threshold, at each frequency tested, from the reference hearing threshold established for normal hearing. The deviation of the threshold, if any, is a measure of the patient's hearing loss.
Manual administration of the pure-tone threshold test has certain advantages. Because the hearing health professional is physically present, he can apply his considerable training and experience during the test. For example, by simply talking to the patient and varying the loudness of his voice, the hearing health professional can determine an initial intensity level at which to start the tones and sounds. Furthermore, the hearing health professional can adapt the pace of the test as needed to accommodate a tired or uncooperative patient. Most importantly, the hearing health professional can discern between false responses or guesses and responses that are legitimate. Finally, the hearing health professional can adjust the results of the hearing test as needed to reflect extenuating circumstances or problems, such as excessive ambient noise, equipment limitations, and other similar factors.
Like most highly trained and specialized medical professionals, however, a hearing health professional's time and services are usually very expensive. Accessibility and convenience can also be issues, as there are fewer hearing health professionals relative to other types of medical professionals. And while hearing health professionals are highly trained, they are limited in their ability to make rapid and accurate calculations of the test data and have to rely on approximations and rules of thumb for guidance in many instances. In addition, few hearing health professionals in the United States can speak a foreign language and, therefore, traditional hearing tests are almost always administered in English, which can be a problem for non-English speaking patients.
Other drawbacks of the traditional, manually administered hearing tests include the need for a quiet room or sound isolation booth in order to properly conduct the tests. The quiet room or sound isolation booth has to comply with ANSI (American National Standards Institute) requirements in terms of how much ambient noise may penetrate the room or booth during a test. Typically, a specially trained technician must evaluate and certify the quiet room or sound isolation booth as meeting ANSI standards before the room or booth can be used. Such testing and/or certification is performed independently of the actual testing administered to a patient, and thus the actual ambient noise levels (and the reliability of the testing) during the testing of a given patient is unknown in current audiometric systems. In addition, there are at present relatively few technicians who are trained to perform such evaluations and certifications. All the above factors combine to increase the complexity of the traditional hearing tests and thereby discourage or at least contribute to a general lack of interest by most people in obtaining regular and frequent hearing tests.
One attempt to simplify the traditional hearing test involves the use of a computer network, such as the Internet, to administer the test. The computer network facilitates interaction between a centralized test administration site and remotely located patient sites. Such an arrangement makes it possible (or at least more convenient) for people in remote or rural areas to obtain a hearing test. The test can also be performed to meet standardized guidelines such as ANSI requirements or certification standards. Despite the increased convenience, however, a hearing health professional still has to manually administer the test, albeit remotely. In this regard, the test is very similar to the traditional hearing test and has many of the same shortcomings, in addition to the fact that the health professional is not physically present.
Accordingly, there is a need for a simpler, less expensive, and more convenient system for air-conduction threshold testing (and other types of hearing tests) that does not compromise the accuracy or thoroughness of the tests. In particular, there is need for an improved system to provide hearing tests that can be self-administered by the patient rather than by the hearing health professional, while retaining the advantages of having a skilled hearing health professional manually administer the test. There is also a need for a system for performing hearing tests that is capable of determining whether ambient noise levels are within acceptable levels during actual patient testing.
In addition to the foregoing limitations associated with audiometric testing, other particular testing limitations preclude widespread hearing testing. One such limitation involves bone-conduction hearing. Because the bones of the skull resonate in response to sound, hearing via bone conduction can be tested in a manner analogous to air conduction. However, instead of pure tones delivered by air conduction through earphones or loudspeakers, bone conduction hearing is tested by delivering sound through a bone-conduction vibrator coupled directly to a bone of the skull, usually the mastoid bone but in some instances the forehead.
Bone conduction testing is clinically significant because differences between the air-conduction and bone-conduction hearing thresholds provides an indication of how much of a hearing loss is attributable to the conductive structures in the outer and middle ear, and how much is attributable to the sensorineural structures of the inner ear and the auditory nerve. However, a reliable bone-conduction test apparatus has proven difficult to obtain because of equipment limitations. In particular, the vibrator element usually is encased in a protective plastic shell that is coupled to a holder, typically either a headset-type spring or a headband. Mastoid-placement bone conduction is particularly difficult because the anatomy of the mastoid makes slippage and/or shifting of the vibrator common. Physiological differences among patients, such as bone contours and fatty deposits in the area, are also more variable at the mastoid than the forehead. Even forehead-conduction bone testing may be difficult, however, not only because of insecure placement and slippage but also because of attenuation of the bone-conduction signal through the holder. Accordingly, there is a need for an improved bone-conduction test apparatus that provides consistent and secure placement, no attenuation, and reliable results.
There is a further need for a system capable of conducting multiple diagnostic hearing tests in a single, convenient system. While many types of diagnostic hearing testing exist, most systems typically are capable of performing only a single test or single type of test. Most audiometer systems, for example, are only capable of performing air-conduction and/or bone-conduction threshold testing. Although some audiometric systems may perform speech recognition testing, there are no commercially available systems capable of conveniently and reliably conducting both audiometric testing and acoustic immittance testing. In addition, there are no systems available for performing both audiometric testing and otoacoustic emission testing.
Inherent in the need for an integrated system for performing multiple diagnostic tests is the need to conduct such tests in a manner that is reliable and convenient for both the hearing health professional and the patient. Merely combining the functionality of an audiometer and an acoustic immittance testing system will provide little benefit if the system is inconvenient to the patient, by for example requiring the patient to use different headphones or ear probes for each test. Instead, there is a need for a system capable of performing multiple diagnostic tests using a single ear probe and an integrated testing system. There is further a need for such systems that are automated to prompt a patient through the tests, while also providing alerts, alarms, notices and other information concerning the tests to a hearing health professional in certain instances.
A convenient multiple diagnostic testing system also implies that the system functionality must be combined in a convenient package that can be quickly and easily coupled to the patient, without a clutter of wires, electrical conduits, transducers and ear probes around the patient. The risk that patient movement would result in damage to one or more wires or conduits in the system is another obstacle to combining multiple diagnostic tests in a single system. In addition, the presence of numerous wires, conduits and probes around the patient can be intimidating and distracting to the patient, in addition to being aesthetically displeasing. Accordingly, there is a need for a system that combines multiple diagnostic tests into a patient interface that can be quickly and easily coupled to the patient, and which provides minimal clutter in the patient environment.